seekdir/telldir bug + fix

Salut,
I have developed a fix for the seekdir/telldir bug which Marc Balmer
discovered recently. I tested it to work on both NetBSD-4.0 and
-current, and it seems to work well and not break anything.
The bug is that if the first entry of a block is deleted, telldir and
seekdir may shoot one entry too far. The patch is of course not to skip
deleted entries when being called from telldir.
I made some adaptions because people told me that this function is
exported and thus 3.0 compatibility would be an issue. I am not sure if
anyone _should_ use it, but since people asked...
I still have to test the compat changes I made though.
Please find the patch under:
http://www.netbsd.org/~tonnerre/patches/src/2008/readdir-no-skip-deleted.patch
A program to reproduce the bug can be found under:
http://www.netbsd.org/~tonnerre/patches/src/2008/readdir-no-skip-deleted.c
Usage: ./readdir-no-skip-deleted 28 2 0
Ok to commit? Or are there modifications which I should make?
Tonnerre